DE2118766C3 - Fluorescent lamp - Google Patents

Description

The present invention relates to fluorescent lamps with amalgam containing lead and bismuth. A lamp of this type is from the German Auslegeschrift 1265 300 known. The amalgam used in this lamp can help reduce due to the mercury vapor pressure, an amalgam poor in mercury and among other metals also contain lead and bismuth.

Also from the Austrian patent specification 131477 is the use of an amalgam made of mercury, Known as lead and bismuth; but here primarily in connection with a discharge vessel, which is operated as a rectifier or gas discharge tube.

The disadvantage of the known fluorescent lamps with amalgam is that their maximum luminous flux is at Temperatures above 30 ° C, i.e. in a temperature range at which fluorescent low-pressure lamps usually not operated. This fact is explained by the low level of mercury The vapor pressure above the well-known amalgams at temperatures below 30 ° C Reduced the intensity of the resonance radiation that causes the fluorescent material to glow.

Pure mercury fluorescent lamps have the maximum of their light output in one area below 30 ° C. However, this is initially disadvantageous the high toxicity and scarcity of mercury. Furthermore, have mercury fluorescent lamps no good constancy of the emitted light emission over the entire service life, d. h., you Luminous flux drops relatively sharply towards the end of the service life. Ultimately, this results in a mercury fluorescent lamp a good light output only in a very narrow temperature range, d. that is, the curve of the luminous flux versus temperature has a relatively sharp maximum.

The object of the present invention is to provide a composition for a fluorescent lamp with amalgam of the amalgam with which optimal operating characteristics at ambient temperatures below 35 ° C and which - compared to cucury fluorescent lamps - have a good conitance the luminous flux over the entire operating time and a good luminous efficacy in a relatively broad Ambient temperature range guaranteed. The amalgam system according to the invention should thereby Suitable for lamps of any power and can be accommodated anywhere in the lamp be able.

Starting from a fluorescent lamp with amalgam of the type mentioned at the beginning, it is proposed for this purpose, that the amalgam consists of 15 to 20 atomic percent mercury, 45 to 75 atomic percent lead and There is 5 to 40 atomic percent bismuth.

Such an amalgam is beard and sufficient Plasticity, so that any dosage in the form of sticks, tablets, spheres, hollow cylinders, Powders and the like can be prepared for introduction into the fluorescent lamp. His Melting temperature is between 200 and 220 ° C.

Under normal conditions the proposed amalgam has a very low mercury activity, whereby optimal operating characteristics of the lamp result and the accumulation of mercury in the operating rooms is excluded.

The choice of amalgam composition within the specified limits depends on the performance the fluorescent lamp off; it is not mandatory to place the amalgam in the lamp.

In order to further explain the invention, exemplary embodiments are described below. The The attached diagram shows the dependence of the luminous flux on the ambient temperature for a 40 W fluorescent lamp with various amalgams and, for comparison, with mercury.

Curves A, B, C shown in the drawing

give an overview of the operation of the fluorescent lamp depending on the percentage of amalgam components mercury, bismuth and Lead.

The table below shows the composition of the three selected amalgams, which are inserted into the mercury fluorescent lamp.

table

Content of components in atomic percent
35

When comparing curves A, B, C one can easily convince oneself that all these curves have a maximum in the temperature range from 30 to 35 ° C. The amalgam with the composition: mercury 20 atomic percent, bismuth 5 atomic percent, lead 75 atomic percent is the most appropriate because its characteristic curve reaches higher temperature values, but the luminous flux slowly decreases. The escape of mercury vapors from the amalgam mainly depends on the lead content, and the lead acts as a certain stabilizer in the formation of the optimum mercury vapor pressure (3 × 10 "Torr) in the lamp. A role is played in the formation of the optimum The formation of intermetallic compounds of mercury and bismuth under the pressure of mercury vapor.

When the lamp is burning, the thermal influence on the amalgam causes the intermetallic to dissolve Mercury-bismuth bond,

A. Ki ng C. mercury
(Hg)
Bismuth (Bi) ..
Lead (Pb) .... 20th
20th
60 15th
10
75 All in all 100 100 lrvenbezeichnu
β 20th
5
75 100

taking an additional reserve of mercury vapors arises in the lamp.

Since the mercury vapor pressure above this amalgam is 20 ° C below IQ " ⁵ Torr, the penetration of mercury vapors into the operating rooms is completely excluded. The amalgam is made of cheap and easily available materials and is characterized by its cost, non-toxicity and operating properties." on known amalgams that were previously used for gas discharge lamps.

The lead, which is part of the composition of this amalgam, acts as a stabilizer for leakage of mercury vapors as it does not form compounds with mercury.

For comparison, the drawing shows you: Characteristic curve D of a fluorescent lamp with mercury for the same output.

1 sheet of drawings

Claims (1)

Claim: Fluorescent lamp with amalgam, the lead and Contains bismuth, characterized in that that the amalgam consists of 15 to 20 atomic percent mercury, 45 to 75 atomic percent lead and consists of 5 to 40 atomic percent bismuth.